Engine cylinder blocks typically include water jackets or passages which generally surround the various cylinder bores and which allow water or coolant to selectively flow around the periphery of the cylinder bores in order to cool the bores. Water jackets therefore allow the heat resulting and/or generated from the combustion processes occurring within the cylinder bores to be dissipated, thereby substantially preventing undesirable heat related structural deformation and/or damage to the cylinder bores and/or to the engine block.
These water jackets are typically formed by the use of a core which is operatively used within the engine block foundry/casting process to form these water/coolant passages or grooves. Particularly, these water jacket cores include an outer portion and one or more "bridge" portions or "bridge" members which are used to form portions of the cylinder bore walls (e.g., those portions positioned between adjacent cylinder bores). These water jacket bridge members therefore define the shape and the size of the created or formed coolant passages which are formed between cylinder bores. The bridge members also ensure that water and/or coolant is allowed to flow between the cylinder bores, thereby increasing the amount by which the bores are selectively cooled.
Typically, each of these water jacket cores are manufactured within a "core box" which defines the desired shape of the core. Particularly, the core box is filled with a mixture of commercially available sand and a commercially available heat curing resin, and is heated at a relatively high temperature until a substantially solidified and cured core is created. Alternatively, the contained sand/resin is "chemically" cured by the use of a chemical catalyst, such as triethylamine ("TEA"), which is selectively placed within the core box and which "sets" or hardens the resin. Once the core is solidified or "set", the core box is opened, "parted" and/or separated, in order to allow the created core to be removed for use in the engine block casting process. There are a number of drawbacks associated with these prior water jacket cores and with their method of manufacture.
First, in order for a core box to be "parted" or separated without substantially damaging the enclosed core, the outer core surfaces and bridge core surfaces must have or form a "draft angle" or an "angle of inclination" of at least one degree with reference to an axis which is perpendicular to the direction in which the main core box is parted. These "draft angles", which are required in order to manufacture the core, result in the creation of relatively thick central core sections residing or formed near the core box parting line and relatively thin core sections formed within those portions of the water jacket remote from the parting line. Particularly, these relatively thick core sections substantially limit or reduce the thickness of the mid-sections or central portions of the created cylinder bore.
After the casting process is complete, as is known, the draft angle of the cores cause an opposite or complementary "angle" to be created and/or formed upon the created cylinder bores. Particularly, this causes each of the created cylinder bores to have a thinner cross-section at their respective mid-sections or mid-portions and a thicker cross-section at their respective top and bottom surfaces. The resultant thin cross-section adversely effects the overall structural integrity of the cylinder bore walls. The thin cross-section of the cylinder bore walls further adversely limits the amount of combustion created pressure which may be produced in the formed engine block without structurally damaging the cylinders. Moreover, the thin cross-section of the bore-walls influences and more particularly, adversely effects or impacts the overall length which may be achieved by the designed cylinder block architecture.
Another drawback related to these prior water jacket cores and their respective method of manufacture is that they do not generally allow for a desirable and substantial increase in the diameter of the cylinder bores. That is, due to the structural limitations of these prior cores and core boxes (e.g., the strength of the core material and draft angle required to be created in these bridge portions), a bridge portion having a minimum thickness of less than 0.139 inches cannot generally be produced (e.g., adjacent outer cylinder bore walls are separated by about 0.139 inches). Therefore, in order to desirably increase the diameter of the cylinder bores (e.g., to increase the power, torque and/or efficiency of the engine), the centers of the bores must be spaced further apart, thereby undesirably increasing the overall length and size of the engine. Another potential alternative is to make the cylinder bore walls thinner, thereby allowing the size or the diameters of the cylinder bores to be increased without increasing the overall length and size of the engine. This potential alternative is undesirable since it substantially and structurally weakens the cylinder bore walls and increases their susceptibility to heat related damage and/or structural deformation.
Another prior technique for increasing the diameter of the cylinder bores is to eliminate the bridge areas within the water jacket core. Unfortunately, this alternative undesirably eliminates the water cooling passages between the cylinder bores. This configuration (i.e., adjacently formed cylinders having no water passages between the cylinders) is typically referred to as a "Siamese" cylinder bore assembly or a "Siamese" type cylinder block. While this approach does increase the cylinder bore diameter, it does not permit the bores to be fully and evenly cooled, thereby potentially causing undesirable heat related cylinder bore metal deformation and/or damage.
There is therefore a need to provide a water jacket core which is formed by a process which allows the water jacket and the formed cylinder block to overcome the various and previously delineated drawbacks of the prior art; which is relatively thinner than typical water jacket cores; and which further includes relatively thin bridge portions, thereby allowing for the use of larger cylinder bores which are substantially and uniformly cooled without increasing the overall engine block architecture.